Grub won't load after windows 10 reset

Question

I had dual boot Windows 10/Ubuntu 14.04. I was resetting my Windows 10 installation and naturally my grub booting menu disappeared. I tried to use boot-repair from Live Ubuntu from USB, but after restart, it still boots the Windows automatically. I can see the original Ubuntu partition from there.

This is the output file http://paste.ubuntu.com/13238347/. I have two disks 128GB SSD and 1TB HDD.

The Windows is NOT hibernating, I have run powercfg -h off and it will boot USB, if the USB is inserted.

I have DISABLED Secure Boot in BIOS.

I did notice something strange however. In my boot order I have my disks first, then USB and then Windows Boot Manager. When I have my bootable USB inserted, it will boot the USB and not the disks, so they can't be booted maybe?

Thanks for any help :)

http://askubuntu.com/a/655279/457247 This was the solution that worked for me — piko, Nov 12 '15 at 15:00
See also this thread: http://askubuntu.com/questions/697195/broken-uefi-boot-how-to-securely-proceed And you may want to houseclean some extra old kernels. — oldfred, Nov 12 '15 at 15:10

cl-netbox · Answer 1 · 2015-11-13T13:46:33.087

As you said you already disabled hibernation in Windows, please re-check this.
Disable Fast Boot : Open Control Panel (the old version - not modern design).
Select Energy Settings - enable show hidden settings - uncheck Fast Boot.
After having done this shutdown the machine completely, do NOT reboot !

Reinstall the GRUB boot loader to your Ubuntu installation in EFI mode.
Boot from the Ubuntu installation media - open a terminal and execute:

    sudo mount /dev/sda7 /mnt
    sudo mount /dev/sda2 /mnt/boot/efi
    for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
    sudo chroot /mnt
    grub-install /dev/sda
    update-grub

Note:

sda = disk | sda2 = efi partition | sda7 = system partition (taken from the pastebin output)

To check and verify the partition numbers use GParted (included in the Ubuntu install media).
Boot into BIOS and select Ubuntu in UEFI settings to be the default operating system to boot.

Grub won't load after windows 10 reset

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